NINA-W1 series - System integration manual
UBX-17005730 - R15
Design-in
Page 33 of 54
C1 - Public
Figure 20: Example of RF trace and ground design from NINA-W1 Evaluation Kit (EVK)
3.3.2
Antenna design (NINA-W1x1)
NINA-W1x1 is suited for designs when an external antenna is needed due to mechanical integration
or placement of the module.
Designers must take care of the antennas from all perspective at the beginning of the design phase
when the physical dimensions of the application board are under analysis/decision, as the RF
compliance of the device integrating NINA-W1 module with all the applicable required certification
schemes heavily depends on the radiating performance of the antennas. The designer is encouraged
to consider one of the u-blox suggested antenna part numbers and follow the layout requirements.
•
External antennas such as linear monopole:
o
External antennas basically do not imply physical restriction to the design of the PCB where
the module is mounted.
o
The radiation performance mainly depends on the antennas. It is required to select antennas
with optimal radiating performance in the operating bands.
o
RF cables should carefully be selected with minimum insertion losses. Additional insertion loss
will be introduced by low quality or long cable. Large insertion loss reduces radiation
performance.
o
A high quality 50
Ω
coaxial connector provides proper PCB-to-RF-cable transition.
•
Integrated antennas such as patch-like antennas:
o
Internal integrated antennas imply physical restriction to the PCB design:
Integrated antenna excites RF currents on its counterpoise, typically the PCB ground plane of
the device that becomes part of the antenna; its dimension defines the minimum frequency
that can be radiated. Therefore, the ground plane can be reduced down to a minimum size that
should be similar to the quarter of the wavelength of the minimum frequency that has to be
radiated, given that the orientation of the ground plane related to the antenna element must
be considered.
The RF isolation between antennas in the system must be as high as possible and the
correlation between the 3D radiation patterns of the two antennas has to be as low as possible.
In general, an RF separation of at least a quarter wavelength between the two antennas is
required to achieve a maximum isolation and low pattern correlation; increased separation
should be considered, if possible, to maximize the performance and fulfil the requirements
described in Table 4.
